It is conventional to form components which are partially or totally of plastic, particularly large components such as vehicle door panels and the like, in a mold press (commonly referred to as a "rim" press) with the part being formed in a mold cavity defined between relatively movable upper and lower mold parts. For forming a component such as a vehicle door panel, various techniques can be utilized. For example, a vinyl sheet which can be heated and vacuumed formed, and possibly in conjunction with a fiberglass sheet, can be positioned in the mold cavity and polyurethane deposited into the cavity to permit molding of the desired component within the press. In some circumstances the vinyl is premolded or preshaped, or in other circumstances the molded component is formed without a vinyl layer.
The conventional mold presses for forming such components are often mounted on a turntable which indexes through a plurality of stations formed along a circular work path. While this arrangement does provide convenience with respect to efficient movement of multiple presses into and through spaced workstations, nevertheless such turntable arrangement typically permits access to the press and specifically to the upper and lower mold parts only from one side, and this greatly hinders and restricts the desired access to the press since workers must access the press so as to not only insert whatever premold parts and components are necessary, but also to assist in removal of the molded part.
As an alternative, many of the known mold presses are freestanding units. This increases worker access by typically permitting access to the press at least from opposite sides thereof. Nevertheless, the overall molding process associated with a single press involves several stages and hence requires significant time, and thus efficient use of workers accordingly normally requires that the workers move back and forth so as to permit servicing of several adjacent freestanding presses. Such arrangement is less efficient than desired, and more fatiguing for workers.
With the known mold presses, as briefly discussed above, the opening and closing movement of the press, as well as the press closure force, is typically controlled by fluid pressure cylinders, normally hydraulic cylinders. Such press arrangements, however, are generally energy inefficient since the use of hydraulic cylinders as the energizing source, and the overall support equipment necessary to provide and supply pressurized hydraulic fluid to the press cylinders, results in significant energy loss in relationship to the electrical energy which is supplied so as to effect operation of the press fluid system. In addition, presses employing hydraulic cylinders for creating the moving and pressing function of the press have also demonstrated an undesirable noise level associated with the fluid cylinder system. Such systems also typically experience leakage of hydraulic fluid, which can create an undesired and sometimes potentially hazardous condition around the press. The hydraulic systems also generate significant and often undesired heat.
In addition, in many of the known mold presses which utilize a movable top platen, the opening and closing movement of the top platen not only typically involves use of hydraulic cylinders, but in addition also typically requires additional complex driving structure, such as an additional driving cylinder, to effect sideward swinging movement of the top platen when in its open position so as to facilitate worker access thereto. The overall drive arrangement for the top platen involves undesired mass and complexity, as well as controls for coordinating the different drives and the different movements provided thereby.
Accordingly, it is an object of this invention to provide an improved mold press which is believed to overcome many of the disadvantages and inconveniences associated with known mold presses, as briefly summarized above, and which is believed to provide for improved efficiency of operation, improved energy efficiency, and improved convenience of access and use.
More specifically, the improved mold press of this invention includes an electric drive arrangement for controlling opening and closing press movement so as to eliminate the use of hydraulic cylinders, whereby the overall energy efficiency of the press is significantly improved, and at the same time, heat generation and oil leakage problems associated with conventional hydraulic cylinder presses are eliminated. The improved mold press and specifically the drive arrangement includes a pair of generally identical drive units connected between the upper and lower press plates. The drive units in a preferred embodiment each employ a ball-screw arrangement. A screw shaft extends vertically of the press, and engages a ball nut assembly which is mounted on the top press plate for effecting movement thereof toward and away from the bottom press plate. An electric motor is coupled to the screw shafts for effecting high speed opening and closing movement of the top press plate. A force apply device, such as an inflatable hose or bladder, is associated with the bottom press plate to effect application of the desired press closing force. A control linkage is connected between the top press plate and the frame for effecting automatic sideward swinging of the top press plate between a side access position when the plate is in its fully opened position, and an operational position wherein the top press plate is disposed vertically aligned above but spaced upwardly from the lower press plate. The swinging movement of the top press plate between these two positions is effected automatically in response to vertical displacement of the top press plate by the main drive unit during an upper portion of the normal opening and closing movement of the top press plate. This control linkage, in a preferred embodiment, comprises a self-contained extendible spring device such as an air spring which effectively assumes a minimum height position when the top press plate is intermediate its stroke so as to induce sideward swinging of the top press plate during the upper portion of the stroke.
In the improved mold press of this invention, as aforesaid, the upper press plate is carried on an upper press platen by a generally horizontally extending pivot which permits sideward vertical swinging of the upper press plate between an operational position wherein it extends generally horizontally and is disposed vertically above the lower press plate, and a sideward access position wherein it is vertically angled so as to project sidewardly to facilitate access by a worker. The upper press platen in turn is vertically slidably supported on the press frame for movement between upper and lower positions which generally correspond to the upper and closed positions of the press. The drive unit and specifically the ball-screw units are connected between the frame and the upper press platen to control movement of the latter. The control linkage is connected between the frame and the upper press plate. When the upper platen is at or below an intermediate position, the control linkage maintains the upper press plate in its operational position so as to permit proper operative positional relationship with the lower press platen. When the upper press platen is being moved vertically between the upper and intermediate positions, however, either during opening or closing of the press, the control linkage is effectively in a solid or noncontractile condition and causes the upper press plate to vertically swing sidewardly into an access position if the upper press platen is being moved upwardly, or conversely causes the upper press platen to be vertically swung sidewardly from the access position to the operational position if the upper press platen is being moved downwardly.
In the improved press of this invention, as aforesaid, the control linkage preferably is formed as a spring unit so that, during movement of the upper press platen between the intermediate position and the lowered (i.e., press closure) position, the spring exerts an upward force on the upper press platen and hence on the upper press plate so as to effectively assist in counterbalancing the weight of the upper press platen during the closing movement, and to create an additive upward force to assist the drive motor during the upward opening movement, the latter being particularly significant with respect to increasing the force which is available to effect initial separation of the upper mold part from the lower mold part.
In accordance with the present invention, as aforesaid, the mold press is preferably mounted on a self-propelled overhead carrier associated with and driven along an overhead rail system so that the mold press is suspended from the carrier and free of direct support from the underlying floor. The overall system preferably includes a plurality of carriers each mounting thereon a mold press, with the carriers being sequentially moved through a plurality of spaced stations along the overhead track, the latter preferably defining a loop, to facilitate efficient use of the presses by permitting various functions to be carried out at spaced workstations, with the presses being efficiently transferred between workstations, and with the actual molding operation being carried out either as the carrier is transferred between workstations or is shuttled into an intermediate holding zone for sufficient duration to permit the desired molding of the component. With the mold press mounted on a driven overhead carrier, the press provides improved access to the mold parts by workers.
Other objects and purposes of the invention will be apparent to persons familiar with assemblies of this general type upon reading the following specification and inspecting the accompanying drawings.